The proposed research constitutes a program of basic research into basic organizational processes in the behavioral development of an altricial mammal, the Norway rat. Because this species is olfactorily dominated the research is designed to elucidate the means by which normal olfactory preferences are formed. In addition, there are a number of studies aimed at basic olfactometric assessment of the development of the sense of smell during early life. Integrated into these investigations is a line of study concerned with early learning processes in the infant, particularly the application of a novel means of heart rate analysis of conditioning. Finally, there is a set of observational studies of mother-litter interactions in an artificial burrow system that is intended to serve as a preliminary test of the reliability and ecological validity of the earlier experiments.